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<html>
<head>
<meta charset='UTF-8'><meta name='viewport' content='width=device-width initial-scale=1'>
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<div  id='write'  class = 'is-node'><h1><a name="service" class="md-header-anchor"></a><span>Service</span></h1><h2><a name="service%E6%B3%A8%E6%84%8F%E4%BA%8B%E9%A1%B9" class="md-header-anchor"></a><span>Service注意事项</span></h2><ol start='' ><li><span>必须使用显式启动来启动Service</span></li><li><span>一个Activity类能有多个实例，但是一个Service类只能有一个实例</span></li><li><span>service同样运行在主线程，那它为什么叫后台？Android的后台就是指，运行过程完全不依赖UI</span></li></ol><h2><a name="service-xml%E5%B1%9E%E6%80%A7" class="md-header-anchor"></a><span>Service xml属性</span></h2><figure><table><thead><tr><th><span>属性</span></th><th><span>作用</span></th></tr></thead><tbody><tr><td><span>enabled</span></td><td><span>服务能否被启动。如果设为</span><strong><span>false</span></strong><span>，虽然不能启动，但也不会抛出异常</span></td></tr><tr><td><span>exported</span></td><td><span>服务能否被其它应用程序调用</span></td></tr><tr><td><span>process</span></td><td><span>让服务运行在别的进程中</span></td></tr></tbody></table></figure><h2><a name="service%E5%90%AF%E5%8A%A8%E6%96%B9%E5%BC%8F" class="md-header-anchor"></a><span>Service启动方式</span></h2><h3><a name="start" class="md-header-anchor"></a><span>start</span></h3><ol start='' ><li><span>onCreate() → onStartCommand() → running → onDestroy()  </span></li><li><span>第一次启动时会调用onCreate()和onStartCommand()，之后再使用startService(Intent)启动服务，只调用onStartCommand()，除非把他StopService(Intent)后，再startService(Intent)；  </span></li><li><span>多次StopService(Intent)只会执行一次onDestroy()，因为他已经被销毁了  </span></li><li><span>onStartCommand(Intent intent, int flags, int startId)的第三个参数是指该方法被调用的次数，也就是说第一次被调用这个传进来的值就是1，后面一次累加，Service运行结束再重新启动后，重新计数</span></li><li><span>stopself()方法可以用来结束start方式启动的service</span></li><li><span>stopSelfResult(int startId)方法也能用来结束service，但是只有当这个startId和onStartCommand的startId的值是相同时，才会结束这个Service</span></li></ol><h3><a name="bind" class="md-header-anchor"></a><span>bind</span></h3><ol start='' ><li><span>onCreate → onBind() → running → onUnbind() → onDestroy()  </span></li><li><span>多个activity可以绑定同一个service，当所有activity都unbind后，这个service就会被destroy  </span></li><li><span>一个service可以既被start又被bind，那么在手动结束他时，需要unbind和stop</span></li></ol><p><span>比如希望一个下载服务可以在后台进行，同时又可以启动一个 Activity 来查看下载进度以及暂停、停止服务，就可以用这种方式。</span><br/><strong><span>如果service已经启动，bindService是同步的，如果为启动则是异步的，对于使用aidl的远程Service还是本进程的service都是一样的</span></strong></p><h3><a name="bindservie%E4%BE%8B%E5%AD%90" class="md-header-anchor"></a><span>bindServie例子</span></h3><p><span>无论在哪个线程绑定服务，onServiceConnected都是在主线程被回调，所以不要在这里执行耗时操作</span></p><pre spellcheck="false" class="md-fences md-end-block md-fences-with-lineno ty-contain-cm modeLoaded" lang="java"><div class="CodeMirror cm-s-inner CodeMirror-wrap" lang="java"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 38px;"><textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea></div><div class="CodeMirror-scrollbar-filler" cm-not-content="true"></div><div class="CodeMirror-gutter-filler" cm-not-content="true"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 34px; margin-bottom: 0px; border-right-width: 0px; padding-right: 0px; padding-bottom: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines" role="presentation"><div role="presentation" style="position: relative; outline: none;"><div class="CodeMirror-measure"></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code" role="presentation" style=""><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><div class="CodeMirror-gutter-background CodeMirror-activeline-gutter" style="left: -34px; width: 34px;"></div><div class="CodeMirror-gutter-wrapper CodeMirror-activeline-gutter" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt CodeMirror-linenumber-show" style="left: 0px; width: 26px;">1</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-comment">//Service的onBind方法中返回一个binder对象，没啥好说的</span></span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">2</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-comment">//有一点是网上的一些简单例子都让自定义的MyBinder中有一个getServie方法来返回一个MyService对象，我觉得这个不可取，binder应该只开放Service的部分接口，而不是全部</span></span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">3</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-keyword">public</span> <span class="cm-keyword">class</span> <span class="cm-def">MyService</span> <span class="cm-keyword">extends</span> <span class="cm-variable">Service</span> {</span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">4</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> &nbsp; &nbsp;<span class="cm-keyword">public</span> <span class="cm-variable">MyService</span>() {}</span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">5</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> &nbsp; &nbsp;<span class="cm-meta">@Override</span></span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">6</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> &nbsp; &nbsp;<span class="cm-keyword">public</span> <span class="cm-variable">IBinder</span> <span class="cm-variable">onBind</span>(<span class="cm-variable">Intent</span> <span class="cm-variable">intent</span>) {<span class="cm-keyword">return</span> <span class="cm-keyword">new</span> <span class="cm-variable">MyBinder</span>();}</span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">7</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> &nbsp; &nbsp;<span class="cm-keyword">class</span> <span class="cm-def">MyBinder</span> <span class="cm-keyword">extends</span> <span class="cm-variable">Binder</span>{</span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">8</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> &nbsp; &nbsp; &nbsp; &nbsp;<span class="cm-variable-3">String</span> <span class="cm-variable">string</span>;</span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">9</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> &nbsp; &nbsp; &nbsp; &nbsp;<span class="cm-keyword">public</span> <span class="cm-variable-3">String</span> <span class="cm-variable">getString</span>() { <span class="cm-keyword">return</span> <span class="cm-variable">string</span>; }</span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt CodeMirror-linenumber-show" style="left: 0px; width: 26px;">10</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> &nbsp; &nbsp; &nbsp; &nbsp;<span class="cm-keyword">public</span> <span class="cm-variable-3">void</span> <span class="cm-variable">setString</span>(<span class="cm-variable-3">String</span> <span class="cm-variable">string</span>) { <span class="cm-keyword">this</span>.<span class="cm-variable">string</span> <span class="cm-operator">=</span> <span class="cm-variable">string</span>; }</span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">11</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> &nbsp;  }</span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt CodeMirror-linenumber-show" style="left: 0px; width: 26px;">12</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;">}</span></pre></div></div></div></div></div></div><div style="position: absolute; height: 0px; width: 1px; border-bottom: 0px solid transparent; top: 260px;"></div><div class="CodeMirror-gutters" style="height: 260px;"><div class="CodeMirror-gutter CodeMirror-linenumbers" style="width: 34px;"></div></div></div></div></pre><pre spellcheck="false" class="md-fences md-end-block md-fences-with-lineno ty-contain-cm modeLoaded" lang="java" style="break-inside: unset;"><div class="CodeMirror cm-s-inner CodeMirror-wrap" lang="java"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 38px;"><textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea></div><div class="CodeMirror-scrollbar-filler" cm-not-content="true"></div><div class="CodeMirror-gutter-filler" cm-not-content="true"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 34px; margin-bottom: 0px; border-right-width: 0px; padding-right: 0px; padding-bottom: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines" role="presentation"><div role="presentation" style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre><div class="CodeMirror-linenumber CodeMirror-gutter-elt"><div>19</div></div></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code" role="presentation" style=""><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><div class="CodeMirror-gutter-background CodeMirror-activeline-gutter" style="left: -34px; width: 34px;"></div><div class="CodeMirror-gutter-wrapper CodeMirror-activeline-gutter" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt CodeMirror-linenumber-show" style="left: 0px; width: 26px;">1</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-comment">//Activity中</span></span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">2</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-variable">MyService</span>.<span class="cm-variable">MyBinder</span> <span class="cm-variable">binder</span>;</span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">3</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-variable">ServiceConnection</span> <span class="cm-variable">connection</span> <span class="cm-operator">=</span> <span class="cm-keyword">new</span> <span class="cm-variable">ServiceConnection</span>() {</span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">4</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> &nbsp; &nbsp;<span class="cm-meta">@Override</span></span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">5</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> &nbsp; &nbsp;<span class="cm-keyword">public</span> <span class="cm-variable-3">void</span> <span class="cm-variable">onServiceConnected</span>(<span class="cm-variable">ComponentName</span> <span class="cm-variable">name</span>, <span class="cm-variable">IBinder</span> <span class="cm-variable">service</span>) {</span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">6</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> &nbsp; &nbsp; &nbsp; &nbsp;<span class="cm-comment">//从AIDL的学习中，我知道这里的service的具体类型就是远程的自定义Binder类型，所以这里直接强制类型转换</span></span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">7</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> &nbsp; &nbsp; &nbsp; &nbsp;<span class="cm-variable">binder</span> <span class="cm-operator">=</span> (<span class="cm-variable">MyService</span>.<span class="cm-variable">MyBinder</span>) <span class="cm-variable">service</span>;</span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">8</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> &nbsp; &nbsp; &nbsp; &nbsp;<span class="cm-variable">binder</span>.<span class="cm-variable">setString</span>(<span class="cm-string">"hello"</span>);</span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">9</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> &nbsp; &nbsp; &nbsp; &nbsp;<span class="cm-variable">Log</span>.<span class="cm-variable">d</span>(<span class="cm-variable">TAG</span>, <span class="cm-string">"onServiceConnected: "</span> <span class="cm-operator">+</span> <span class="cm-variable">binder</span>.<span class="cm-variable">getString</span>());</span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt CodeMirror-linenumber-show" style="left: 0px; width: 26px;">10</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> &nbsp;  }</span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">11</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> &nbsp; &nbsp;<span class="cm-meta">@Override</span></span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">12</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> &nbsp; &nbsp;<span class="cm-keyword">public</span> <span class="cm-variable-3">void</span> <span class="cm-variable">onServiceDisconnected</span>(<span class="cm-variable">ComponentName</span> <span class="cm-variable">name</span>) {}</span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">13</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;">};</span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">14</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-meta">@Override</span></span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">15</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-keyword">protected</span> <span class="cm-variable-3">void</span> <span class="cm-def">onCreate</span>(<span class="cm-variable">Bundle</span> <span class="cm-variable">savedInstanceState</span>) {</span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">16</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> &nbsp; &nbsp;<span class="cm-keyword">super</span>.<span class="cm-variable">onCreate</span>(<span class="cm-variable">savedInstanceState</span>);</span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">17</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> &nbsp; &nbsp;<span class="cm-variable">setContentView</span>(<span class="cm-variable">R</span>.<span class="cm-variable">layout</span>.<span class="cm-variable">activity_main</span>);</span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt" style="left: 0px; width: 26px;">18</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> &nbsp; &nbsp;<span class="cm-variable">bindService</span>(<span class="cm-keyword">new</span> <span class="cm-variable">Intent</span>(<span class="cm-keyword">this</span>,<span class="cm-variable">MyService</span>.<span class="cm-keyword">class</span>), <span class="cm-variable">connection</span>, <span class="cm-variable">Context</span>.<span class="cm-variable">BIND_AUTO_CREATE</span>);</span></pre></div><div style="position: relative;"><div class="CodeMirror-gutter-wrapper" style="left: -34px;"><div class="CodeMirror-linenumber CodeMirror-gutter-elt CodeMirror-linenumber-show" style="left: 0px; width: 26px;">19</div></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;">}</span></pre></div></div></div></div></div></div><div style="position: absolute; height: 0px; width: 1px; border-bottom: 0px solid transparent; top: 380px;"></div><div class="CodeMirror-gutters" style="height: 380px;"><div class="CodeMirror-gutter CodeMirror-linenumbers" style="width: 34px;"></div></div></div></div></pre><p><span>bindService方法的第三个参数</span><code>Context.BIND_AUTO_CREATE</code><span>的意思是如果要绑定的服务不存在就创建它，同时它还是决定服务是否需要被unbind后才能结束的根本因素。</span><br/><strong><span>“如果程序既被start有被bind，那结束它就需要既unbind又stop”</span></strong><span>，这句话的前提是bindService使用的flag是</span><code>Context.BIND_AUTO_CREATE</code><span>，如果这个flag是其它的，比如0，那就直接stop，即可结束服务，而且由于flag是0，所以如果服务未启动是不会被创建的，所以需要先start，而不能直接bind。</span><br/><span>当然还有其它flag，有机会再了解</span></p><h2><a name="intentservice" class="md-header-anchor"></a><span>IntentService</span></h2><p><span>service也是运行在主线程中的，所以如果在他里面执行耗时的操作也是或报ANR异常的。要解决这个问题可以在service中开一个子线程，或者不使用service而是使用它的子类——IntentService  </span></p><h3><a name="intentservice%E7%9A%84%E7%89%B9%E7%82%B9" class="md-header-anchor"></a><span>IntentService的特点</span></h3><ol start='' ><li><span>他会单独创建一个子线程，来处理所有发给他的Intent请求</span></li><li><span>这些Intent请求会被放在队列中，依次执行</span></li><li><span>客户端的stopService或IntentService的stopSelf都不能停止IntentService，虽然它的onDestory会被调用，但是他并没有停止，它会在所有Intent请求都被处理后自动结束</span></li><li><span>我只需要重写IntentService的onHandleIntent方法即可，不用重写其他方法</span></li></ol><h2><a name="%E5%89%8D%E5%8F%B0service" class="md-header-anchor"></a><span>前台Service</span></h2><p><span>不同于IntentService，前台Service不是一个具体的类，它是Service与notification的组合。</span><br/><span>前台service通过notification与用户交互，即使在内存不足的情况下它也不会被杀死。</span><br/><span>前台服务必须是start方式启动的服务，（我觉得既start又bind的也可以）。</span></p><p><span>把一个后台服务变成前台很简单，就是使用</span><code>startForeground (int id, Notification notification)</code><span>（一般是在onStartCommand中），第一个参数是notification的id，第二个是要展示的notification对象。</span><br/><span>用</span><code>stopForeground (int flags)</code><span>或者</span><code>stopForeground (boolean removeNotification)</code><span>可以把前台服务变回后台（一般在onDestory中），两者效果一样，但是建议用后者，因为旗标难记，后者的参数就很简单——变为后台时是否删除原先的通知。</span></p></div>
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